1. Field of the Invention
The present invention generally relates to a slide rail device for use in a vehicle seat such an automotive seat, which is operable to adjust the seat in position in the fore-and-aft direction. More specifically, the invention is directed to the slide rail device of this kind for particular use in a foldable type of vehicle seat provided with a seat belt anchor.
2. Description of Prior Art
In general, a slide rail device is provided for adjustment of fore-and-aft position of a vehicle or automotive seat. In the case where the slide rail device is applied to a vehicle seat of the kind having a seat belt anchor for anchoring a seat belt which restrains the body of an occupant to the seat, a structural reinforcement is arranged in the slide rail device to resist a great pulling force applied from the occupant through the seat belt in a collision case or the like. As a typical conventional arrangement in this regard, either of the upper and lower rails of slide rail device may be increased in thickness, or a reinforcing element may be provided thereto, so as to prevent separation of the upper rail from the lower rail due to the foregoing great pulling force.
The slide rail device of this kind is also used in a second seat within the so-called "one-box car" or van-type automobile which normally has three sets of seats disposed therein; i.e. a front seat, a second seat and third seat. The second seat is therefore of the foldable type that allows its seat back to be folded onto its seat cushion and further allows the whole seat to be jumped or turned via a hinge in the forward direction to an inverted upright state, so that an increased space may be attained in the cabin, as a load carrying area for example. As known in the art, the slide rail device comprises a lower rail member fixed on a floor of vehicle or automobile, and an upper rail member slidably fitted in the lower rail member, on which upper rail member, the seat is mounted. In particular, rollers are provided between the lower and upper rail members to improve the slidability of the upper rail member along the lower rail member, and the rollers are normally composed of a forward set of rollers disposed forwardly of the slide rail device and a rearward set of rollers disposed rearwardly of the same.
These hitherto structures of slide rail device, however, have been found defective in that its weight is increased and the number of associated fittings and parts are also increased, with a complicated designs incidental therewith, hence requiring a number of additional assembling steps and man hours. Further, when the upper rail member are slid forwards and projected from the lower rail member, the forward set of rollers are exposed away from the lower rail member, in which case, the projected portion of upper rail member are fallen in contact with the bottom of lower rail member, interfering with the smooth forward sliding of the upper rail member along the lower rail member. This contact also interferes with backward sliding of the upper rail member. In that case, the exposed rollers collide with the forward edges of lower rail member, which prevents further backward sliding of upper rail member, with the result that the upper rail member can hardly be slid back to a home position upon the lower rail member.